Sistema de valoración propuesto para Colombia

The proportions of beetles positive for Cry1Ab (refuge corn) were greatest in 20%

structured refuge treatments and lowest in 0% structured refuge treatments each year; in 2011 and 2012, there was no difference between the 5% structured refuge and 5% seed blend

treatments, while in 2010 the proportion of Cry1Ab positive beetles was greater in 5% structured refuge than 5% seed blend treatments (2010: χ² = 374.03, df = 3, P < 0.0001; 2011: χ² = 330.82, df = 3, P < 0.0001; 2012: χ² = 326.55, df = 3, P < 0.0001). The proportions of Cry1Ab positive beetles were greater during the vegetative period than the pollination period and lowest during the post-pollination period each year (2010: χ² = 328.19, df = 2, P < 0.0001; 2011: χ² = 203.83, df = 2, P < 0.0001; 2012: χ² = 222.77, df = 2, P < 0.0001). Row-by-row multiple comparisons revealed that, in structured refuge treatments, the proportions of beetles testing positive for Cry1Ab were greatest in refuge rows throughout the season (Figures 3.1 through 3.3). Cry1Ab positive beetles were collected in some Bt rows during the vegetative period of corn phenology,

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but the proportion of beetles testing positive for refuge corn diminished as the distance between each sampling row and the refuge increased (Figures 3.1 through 3.3). As corn phenology progressed, the proportions of Cry1Ab positive beetles collected in Bt rows diminished (Figures 3.1 through 3.3).

The proportions of beetles positive for Cry1F (Bt corn) were greatest in 0% structured refuge treatments and lowest in 20% structured refuge treatments each year (2010: χ² = 275.44, df = 3, P < 0.0001; 2011: χ² = 322.54, df = 3, P < 0.0001; 2012: χ² = 334.31, df = 3, P < 0.0001).

In 2010 and 2011, the proportions of Cry1F positive beetles were greater during the pollination period than the post-pollination period and lowest during the vegetative period each year (2010:

χ² = 111.88, df = 2, P < 0.0001; 2011: χ² = 171.91, df = 2, P < 0.0001). In 2012, there were no differences in the proportions of Cry1F positive beetles during the pollination and

post-pollination periods, but they were significantly lower during the vegetative period (2012: χ² = 222.77, df = 2, P < 0.0001). Row-by-row multiple comparisons revealed that the proportions of beetles positive for Cry1F were greatest in Bt rows and did not differ among the rows throughout the pollination and post-pollination periods. During the vegetative period, the proportions of beetles positive for Cry1F were also greater in Bt rows although there was some variation among Bt rows with low beetle abundance (Figures 3.1 through 3.3).

In 5% seed blend treatments, low proportions of Cry1Ab positive beetles were collected in nearly every corn row throughout the season; those proportions did not differ among the rows (Figures 3.1 through 3.3). Few Cry1Ab positive beetles were collected in any 0% refuge

treatment sampling rows; most were collected during the vegetative period (Figures 3.1 through 3.3). The proportions of Cry1Ab positive beetles in 0% refuge treatments diminished during the pollination and post-pollination periods (Figures 3.1 through 3.3). The proportions of Cry1F

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positive beetles collected in the 5% seed blend and 0% refuge treatments did not differ among sampling rows and remained high across the phenology periods (Figures 3.1 through 3.3). As with structured refuge treatments, the row-to-row variability in the proportion of Cry1F positive beetles in 5% seed blend and 0% refuge was greatest during the vegetative period.

The proportions of intrafield movers

Each year, there was no difference in the mean proportion of beetles that were “movers”

between refuge and Bt corn in 20% and 5% structured refuge treatments (2010: χ² = 0.72, df = 1, P = 0.3950; 2011: χ² = 0.25, df = 1, P = 0.6136; 2012: χ² = 0.10, df = 1, P = 0.7477; Table 3.1).

However, significantly more movers were identified during the vegetative period than during pollination or post-pollination (2010: χ² = 92.38, df = 2, P < 0.0001; 2011: χ² = 171.23, df = 2, P

< 0.0001; 2012: χ² = 52.83, df = 2, P < 0.0001; Table 3.2).

The direction of travel was also considered. With respect to movement from refuge to Bt corn in structured refuges, the mean proportion of movers was greater in 20% structured refuges than 5% structured refuges in 2010 and 2011 (2010: χ² = 7.10, df = 1, P = 0.0077; 2011: χ² = 4.34, df = 1, P = 0.0372; Table 3.1) but there was no difference in the proportion of movers between those treatments in 2012. A greater proportion of beetles also moved from refuge to Bt corn during the vegetative period when compared to the pollination and post-pollination periods (2010: χ² = 118.50, df = 2, P < 0.0001; 2011: χ² = 108.89, df = 2, P < 0.0001; 2012: χ² = 56.63, df = 2, P < 0.0001; Table 3.2).

Regarding beetles moving from Bt corn into the refuge, the mean proportion traveling from Bt corn to refuge corn was greater in the 5% structured refuge than the 20% structured refuge each year (2010: χ² = 4.19, df = 1, P = 0.0406; 2011: χ² = 20.24, df = 1, P < 0.0001; 2012:

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χ² = 17.44, df = 1, P < 0.0001; Table 3.1) and there was no impact of corn phenology on these proportions (Table 3.2).

The mean proportion of double positive beetles (those testing positive for both refuge and Bt corn Cry proteins) was influenced by refuge treatment each year (2010: χ² = 45.62, df = 3, P <

0.0001; 2011: χ² = 166.44, df = 3, P < 0.0001; 2012: χ² = 201.30, df = 3, P < 0.0001). In 2010, there was no difference in the mean proportion of double positives among the 20% structured, 5% structured or 5% seed blend refuge treatments and each was greater than the proportion in the 0% refuge treatments (Table 3.3). In 2011 and 2012, the 5% seed blend treatments had the greatest mean proportion of double positive beetles (Table 3.3). The 20% structured and 5%

structured refuge treatments did not differ and the 0% refuges had the lowest proportion of double positive beetles (Table 3.3).

Estimations of daily movement rates

When beetles moved from refuge to Bt corn, they traveled at 26.23 ± 3.09 m/d in 2010, 30.31 ± 2.34 m/d in 2011 and 31.22 ± 2.43 m/d in 2012. Rate of movement did not differ between 20% and 5% structured refuge treatments, except in 2010, when the movement rate for the 20% structured refuge treatments, 32.28 ± 4.46 m/d, was greater than that for 5% structured refuge treatments, 19.43 ± 4.10 m/d (F = 4.43, df = 1, 135, P = 0.04). During 2011, movement rates in 20% and 5% structured refuge treatments were 29.60 ± 3.00 m/d and 31.30 ± 3.74 m/d, respectively. During 2012, movement rates in 20% and 5% structured refuge treatments were 30.38 ± 2.81 m/d and 32.62 ± 4.50 m/d, respectively. Corn phenology did not affect the rate of travel in 2010 but was a significant factor in 2011 (F = 5.90, df = 2, P = 0.0032) and 2012 (F = 4.16, df = 2, P = 0.0170). In 2010, beetles traveled 28.35 ± 4.28 m/d during the vegetative

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period, 25.07 ± 6.52 m/d during the pollination period and 21.91 ± 6.07 m/d during post-pollination. In 2011, the rate of travel was greatest during the pollination period when they moved 50.33 ± 7.17 m/d compared to the vegetative and post-pollination periods when beetles moved 24.58 ± 2.49 m/d and 28.93 ± 4.78 m/d, respectively. In 2012, beetles traveled at the greatest rate during the post-pollination period at 42.24 ± 5.77 m/d and at the lowest rate during the vegetative period at 24.76 ± 3.15 m/d. During the pollination period, beetles traveled 32.32 ± 4.36 m/d, which did not differ from either the vegetative or post-pollination periods.

Interfield movement

The mean proportion of males collected in sampling rows that originated from an offsite location (Cry3Bb1 positive males) was annually influenced by the phenology (2011: χ² = 32.41, df = 2, P < 0.0001; 2012: χ² = 63.72, df = 2, P < 0.0001). The greatest proportion of Cry3Bb1 positive males was collected during the vegetative period while the Cry3Bb1 positive

proportions collected in the pollination and post-pollination periods did not differ (Table 3.2).

DISCUSSION